The Present Perfect

The present perfect: (Time until now)

For irregular verbs, the past participle and the simple past,
are sometimes the same. But for regular verbs they are 
always the same.

For the present perfect, the  situation that started in the past 
is always connected with the present. Started in the past, but 
it's not complete(time from the past until now).

• A fact that happened in the past, but we are not interested in when it happened,

  Examples:

  She has gone to Mexico.
  They have been in university.
  
  
• A new fact,

  Examples:

  I have got a new car
  Has the test occurred?
  
  
• A situation that is in progress. A situation started in the past and continues in the present (and will probably continues into the future). This is a state (not an action). We usually use for or since with this structure.
  

  Examples:

  She has slept since 6 O'clock.
  They have been ill for 2 days.
  How long have you known him?
  

For is related to a period of time: 6 hours minutes, 7 weeks, 15 year, etc It means: from the beginning of the period until the end of the period.
• For is used for all tenses. It is not used with: all + period:
  He slept all the day.
  
• Since is related to a point of time: 7 o'clock, 1st June, Friday, etc
  Since means: from the point in the past until now.
  Since is used for Perfect tenses.
  Since can also be used in this structure: It is (period) since...
  It’s twenty minutes since I start this test.
  

We use for and since to say how long. But If we need to know the time 
of the beginning of an action we say When or What time. For this adverb,
we use ago (Before now) for the answer and in simple past

Examples

• When did he arrive home? (Past) He arrived home at six o'clock.
  He arrived home three hours ago.
  
• How long has he been home? He's (has) been home for three hours.
  (Since 6:00 PM. Now it's 9:00PM)

We use the present perfect with EVER and NEVER

Examples:

Other examples:

• Where have you been Joe? We haven't seen you for ages!
• Where has she gone? = Where is she (now)?
• Where has she been? (When she will arrive?).
  Right now, you are (present) home.
  
• How long have you been home?
  - You have been (present perfect) home since 6:00 PM
  - You have been (present perfect) home for 3 hours (It’s 9:00 PM)
  
• How long have you been interested in English? (You are interested: passive)
• How long have you known this person? (You know: active)
• How long did she live in Saskatoon? (She lived)
• How long has she lived in Saskatoon? (She has lived)
• How long has she been living in Saskatoon? (She is living):
  
  This is The present perfect continuous.

The present perfect continuous:

• An action that has just stopped or recently stopped. We have a result now.

  Examples:

  I'm late (now) because I've been sleeping. Why are you so tired (now)?
  Have you been working?
  You don't understand (now) because you haven't been listening.
  
  
• An action that is continuing. We used with for or since.

  Examples:

  I have been reading for 2 hours. (I am still reading now.)
  We've been studying since 9 o'clock. (We’re still studying now.)
  How long have you been learning English? (You are still learning now.)
  We have not been smoking. (And we are not smoking now.)

Remark: